CONTACTLESS COMMUNICATION CIRCUIT AND PORTABLE TERMINAL

• US 20080012712A1
• Filed: 07/06/2007
• Published: 01/17/2008
• Est. Priority Date: 07/14/2006
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Ericsson Mobile Communications Japan Incorporated (Sony Group Corp.)
• Inventors: SHIMIZU, Kanjiro
• Granted Patent: US 7,907,056 B2
• Time in Patent Office: Days
• US Class Current: 340/572.5
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 7/10237 the reader and the record carrier being capable of selectively switching between reader and record carrier appearance, e.g. in near field communication [NFC] devices where the NFC device may function as an RFID reader or as an RFID tag
• CPC Class Codes: H04B 5/22 Capacitive coupling
• CPC Class Codes: H04B 5/77 for interrogation

Abstract

The present invention provides a contactless communication circuit having both a contactless communication card function and a contactless communication reader/writer function, which includes a capacitor section that forms a parallel-resonant circuit with a contactless communication antenna; and a capacitance switching section that makes a capacitance of the capacitor section effective in a mode of the contactless communication card function, and reduces the capacitance of the capacitor section in a mode of the contactless communication reader/writer function.

Claims

1. A contactless communication circuit having both a contactless communication card function and a contactless communication reader/writer function, comprising:

a capacitor section that forms a parallel-resonant circuit with a contactless communication antenna; and

a capacitance switching section that makes a capacitance of the capacitor section effective in a mode of the contactless communication card function, and reduces the capacitance of the capacitor section in a mode of the contactless communication reader/writer function.

2. The contactless communication circuit according to claim 1, wherein:

the capacitor section is a capacitor connected at one end thereof to one end of the contactless communication antenna, and

the capacitance switching section has;

a first field-effect transistor inserted between the other end of the capacitor and a ground,

a second field-effect transistor inserted between the other end of the contactless communication antenna and a ground, and

a control section that turns on the first and second field-effect transistors in the mode of the contactless communication card function and turns off the first and second field-effect transistor in the mode of the contactless communication reader/writer function.

3. A contactless communication circuit having both a contactless communication card function and a contactless communication reader/writer function, comprising:

a main antenna connected to a main circuit for contactless communication;

a sub-antenna coupled with the main antenna;

a capacitor section that forms a parallel-resonant circuit with the sub-antenna; and

a capacitance switching section that makes a capacitance of the capacitor section effective in a mode of the contactless communication card function, and reduces the capacitance of the capacitor section in a mode of the contactless communication reader/writer function.

4. The contactless communication circuit according to claim 3, wherein:

the capacitor section is a capacitor that forms the parallel-resonant circuit with the sub-antenna, and

the capacitance switching section has;

a field-effect transistor connected within the parallel-resonant circuit formed of the capacitor and the sub-antenna, and

a control section that turns on the field-effect transistor in the mode of the contactless communication card function and turns off the field-effect transistor in the mode of the contactless communication reader/writer function.

5. The contactless communication circuit according to claim 3, wherein:

the capacitor section is a capacitor that forms the parallel-resonant circuit with the sub-antenna, and

the capacitance switching section has;

a field-effect transistor inserted between a ground and a node between the capacitor and the sub-antenna, and

a control section that turns on the field-effect transistor in the mode of the contactless communication card function and turns off the field-effect transistor in the mode of the contactless communication reader/writer function.

6. A contactless communication circuit having at least a contactless communication reader/writer function, comprising:

a capacitor connected at one end thereof to one end of a contactless communication antenna;

a first field-effect transistor inserted between the other end of the capacitor and a ground;

a second field-effect transistor inserted between the other end of the contactless communication antenna and a ground; and

a control section that turns on the first and second field-effect transistors when communicating with an anticollision contactless communication card, and turns off the first and second field-effect transistors when communicating with a non-anticollision contactless communication card.

7. A contactless communication circuit having at least a contactless communication reader/writer function, comprising:

a main antenna connected to a main circuit for contactless communication;

a sub-antenna coupled with the main antenna;

a capacitor that forms a parallel-resonant circuit with the sub-antenna;

a field-effect transistor connected within the parallel-resonant circuit formed of the capacitor and the sub-antenna; and

a control section that turns on the field-effect transistor when communicating with an anticollision contactless communication card, and turns off the field-effect transistor when communicating with a non-anticollision contactless communication card.

8. A contactless communication circuit having at least a contactless communication reader/writer function, comprising:

a main antenna connected to a main circuit for contactless communication;

a sub-antenna coupled with the main antenna;

a capacitor that forms a parallel-resonant circuit with the sub-antenna;

a field-effect transistor inserted between a ground and a node between the capacitor and the sub-antenna; and

a control section that turns on the field-effect transistor when communicating with an anticollision contactless communication card, and turns off the field-effect transistor when communicating with a non-anticollision contactless communication card.

9. A portable terminal having both a contactless communication card function and a contactless communication reader/writer function, comprising:

a capacitor section that forms a parallel-resonant circuit with a contactless communication antenna;

a capacitance switching section that switches a capacitance of the capacitor section; and

a control section that controls the capacitance switching section to make the capacitance of the capacitor section effective in a mode of the contactless communication card function, and controls the capacitance switching section to reduce the capacitance of the capacitor section in a mode of the contactless communication reader/writer function.

10. A portable terminal having both a contactless communication card function and a contactless communication reader/writer function, comprising:

a main antenna connected to a main circuit for contactless communication;

a sub-antenna coupled with the main antenna;

a capacitor section that forms a parallel-resonant circuit with the sub-antenna;

a capacitance switching section that switches a capacitance of the capacitor section; and

a control section that controls the capacitance switching section to make the capacitance of the capacitor section effective in a mode of the contactless communication card function, and controls the capacitance switching section to reduce the capacitance of the capacitor section in a mode of the contactless communication reader/writer function.

11. A portable terminal having at least a contactless communication reader/writer function, comprising:

a capacitor connected at one end thereof to one end of a contactless communication antenna;

a first field-effect transistor inserted between the other end of the capacitor and a ground;

a second field-effect transistor inserted between the other end of the contactless communication antenna and a ground; and

a control section that turns on the first and second field-effect transistors when communicating with an anticollision contactless communication card, and turns off the first and second field-effect transistors when communicating with a non-anticollision contactless communication card.

12. A portable terminal having at least a contactless communication reader/writer function, comprising:

a main antenna connected to a main circuit for contactless communication;

a sub-antenna coupled with the main antenna;

a capacitor that forms a parallel-resonant circuit with the sub-antenna;

a field-effect transistor connected within the parallel-resonant circuit formed of the capacitor and the sub-antenna; and

a control section that turns on the field-effect transistor when communicating with an anticollision contactless communication card, and turns off the field-effect transistor when communicating with a non-anticollision contactless communication card.

13. A portable terminal having at least a contactless communication reader/writer function, comprising:

a main antenna connected to a main circuit for contactless communication;

a sub-antenna coupled with the main antenna;

a capacitor that forms a parallel-resonant circuit with the sub-antenna;

a field-effect transistor inserted between a ground and a node between the capacitor and the sub-antenna; and

a control section that turns on the field-effect transistor when communicating with an anticollision contactless communication card, and turns off the field-effect transistor when communicating with a non-anticollision contactless communication card.